The present application claims priority to Japanese Patent Application No. 2002-018749 filed in the Japanese Patent Office on Jan. 28, 2002 and Japanese Patent Application No. 2002-381426 filed in the Japanese Patent Office on Dec. 27, 2002, the disclosures of which are hereby incorporated by reference herein in their entirety.
1. Field of the Invention
The present invention relates to an electrophotographic color image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multi-functional image forming apparatus, and more particularly to an image carrier driving mechanism that drives an image carrier in the image forming apparatus to rotate.
2. Discussion of the Background
A multi-color image forming apparatus that forms multi-color (two or more colors) images on a transfer material, such as a transfer sheet, and an overhead transparency film, includes two or more sets of charging devices, exposure devices, and developing devices around an image carrier. In such a multi-color image forming apparatus, an image forming process including charging, exposing, and developing steps is repeated while the image carrier is rotated, and toner images of different colors are superimposed upon each other on the image carrier. Subsequently, superimposed toner images are collectively transferred from the image carrier to a transfer material.
In the above-described multi-color image forming apparatus, a drive force of a drive motor serving as a drive device is conveyed to the image carrier via gears and/or a timing belt spanned around timing pulleys in an image carrier driving mechanism. However, in a multi-color image forming apparatus including such an image carrier driving mechanism, irregular rotation of the image carrier caused by the eccentricity and irregular shape of meshing members such as gears and timing pulleyscauses unevenness of image density and displacement of color images of toner images on a transfer material, thereby deteriorating image quality.
In order to solve the above-described problem, for example, Japanese Laid-open patent application No. 9-81006 describes a color image forming apparatus in which the timing of exposure performed by an image exposure device is controlled based on information of a rotational fluctuation of an image carrier.
Further, Japanese patent No. 2745599 describes a multi-color image recording apparatus in which each image forming unit is arranged at a position corresponding to the same phase of the rotary variation cycle of a transfer material carrier.
Moreover, Japanese Laid-open patent application No. 2000-98690 describes a multicolor image forming apparatus in which displacement of color images is prevented by regulating the number of teeth of gears in an image carrier driving mechanism.
However, the structure of the above-described background apparatus tends to be complicated.
According to one aspect of the present invention, an image forming apparatus includes an image carrier rotatably provided therein and configured to carry an image on a circumferential surface of the image carrier, at least one exposure device configured to expose a plurality of exposure positions on the circumferential surface of the image carrier with light, a drive device configured to drive the image carrier to rotate, a first meshing member positioned to rotate coaxially and unitarily with the image carrier, a second meshing member positioned to convey a drive force generated by the drive device to the first meshing member by one of a direct meshing engagement with the first meshing member and a timing belt spanned around the first and second meshing members. The first meshing member has a plurality of teeth between first and second exposure positions of the plurality of exposure positions, and the plurality of teeth on the first meshing member has a number of teeth which is an integer multiple of a number of teeth on the second meshing member.
According to another aspect of the present invention, an image forming apparatus includes an image carrier rotatably provided therein and configured to carry an image on a circumferential surface of the image carrier, at least one exposure device configured to expose a plurality of exposure positions on the circumferential surface of the image carrier with light, a drive device configured to drive the image carrier to rotate, a first meshing member positioned to rotate coaxially and unitarily with the image carrier, second meshing member positioned to convey a drive force generated by the drive device to the first meshing member via a timing belt spanned around the first and second meshing members, and a tension roller positioned to press against a surface of the timing belt to tension the timing belt. The timing belt has a conveyance distance between the first and second exposure positions, and the conveyance distance is an integer multiple of a peripheral length of the tension roller.
According to yet another aspect of the present invention, an image forming apparatus includes an image carrier rotatably provided therein and configured to carry an image on a circumferential surface of the image carrier, at least one exposure device configured to expose a plurality of exposure positions on the circumferential surface of the image carrier with light, a drive device configured to drive the image carrier to rotate, at least one pair of meshing members positioned to convey the drive force generated by the drive device to the image carrier, and a cleaning device configured to clean the circumferential surface of the image carrier while being driven by the drive device to slide in a longitudinal direction of the cleaning device. The image carrier is rotated between the first and second exposure positions for a time which is an integer multiple of a time for sliding the cleaning device by one reciprocating motion.